Enhanced effect of thermal expansion process in rotational shear technology for high performance HDPE pipes

The purpose of this paper is to study the effect of thermal expansion process and rotational shear on the structure and properties of high-density polyethylene (HDPE) pipes. In this paper, HDPE pipes with excellent properties were prepared by the rotational shear system (RSS) and the thermal expansion process. The morphology study results showed that shish-kebab crystals appeared in the pipes. And with the application of thermal expansion process, the interlocking degree of the shish-kebab crystals was further deeper. The thickness of kebab increased greatly and a certain degree of tilt occurred. With the increase of the tensile ratio, the mechanical properties were improved. When the tensile ratio was 1.25, the hoop tensile strength of the pipes increased by 31.50%, and the creep rate also increased by 67.44%. The better mechanical properties at the tensile ratio of 1.25 are mainly attributed to the tighter Shish-Kebab structure after tube expansion. [Display omitted] •A systematic shish-kebab structure study of HDPE pipes under shear field and thermal expanding process is reported.•With the application of thermal expansion process, the interlocking degree of the Shish-Kebab crystals is further deeper.•The enhanced hoop strength and heat properties have been confirmed.